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By Leonard D. Jaffe

IN recent years, the advantages of tempered martensite as a microstructure for steel parts have been well established. For parts that must not fracture brittlely when loaded at high rates, at low temperatures, or under conditions of combined stress, tempered martensite is especially desirable. One of the factors that determine whether a steel part will have a martensitic structure after heat treatment is the hardenability of the steel. Despite the large amount of recent research, there are still many unsettled basic questions concerning hardenability and its relation to chemical composition, and, indeed, considerable disagreement among investigators in the field. Much of the uncertainty that beclouds the existing knowledge of hardenability arises from the fact that hardenability is still a wholly empirical concept, and has not been quantitatively related to the more fundamental knowledge of isothermal decomposition of austenite. Hardenability is, essentially, a measure of the time required for small percentages of austenite to decompose, during continuous cooling, to pearlite, bainite, proeutectoid ferrite, or proeutectoid carbide. In the practical heat-treatment of steel, also, the decomposition of austenite is usually not isothermal but rather during cooling, or, in general, is not at a single constant temperature. Thus, both hardenability and practical heat treatment involve anisothermal decomposition of austenite. In a previous publication1 the author and his collaborators outlined the principles that govern the relations between isothermal and anisothermal decomposition of austenite, and reviewed the experimental information available in 1945. To avoid repetition, familiarity with that article (Paper 1) will be assumed, and attention given primarily to work carried out or published since 1945. The method generally employed was explained in Paper 1: anisothermal transformation is studied through investigation of the effect of holding austenite at one temperature upon its subsequent decomposition at another temperature. Both temperatures are below the stability range of the austenite. This paper is confined to studies in which only a small amount of transformation occurred at the first temperature. This is the only case of importance in practical heat treatment when an essentially martensitic structure is sought. MATERIALS AND PROCEDURE It was necessary to use different steels for the studies involving proeutectoid ferrite and for those involving proeutectoid carbide, because the two constituents have not been found to form in the same steel. Several steels were tried and rejected

Jan 1, 1947

AS provided in Article VIII, Section 4 of the By- laws, the Papers and Publications Committee has formulated the following, rules of pro-cedure and submitted them to the Board of Directors for consideration and approval. In preparing these rules the committee, and an active subcommittee con-sisting of Messrs. Norris, Sharpless; Fohs and Wither-ell, have kept in mind the desirability of codifying the practice that has grown up through the now sev-eral years of experience of the committtee, without casting them in a mold so rigid as to be hampering. The problems of the Institute change from year to year and the methods of publication must change also to meet each new situation as it arises. "The estab-lishment of divisions and special volumes devoted to the papers. read before each required certain changes from former practice. These rules have been framed with this in view. The committee suggested, however, in its letter of transmittal, that the system will be made all the more workable if the Board will, as far as practicable, in making appointments to this committee, arrange for representation from each of the professional divisions and technical committees. It is understood that the chairman of the committee will be named by the Board. The rules regarding spe-cial volumes have been framed, keeping in mind the present policy of distribution, as already approved by the Directors under which the special volumes go only to the special. groups except on request. The committee has not attempted to provide rules governing consideration of any appeal made to the Board from one of its decisions, but its services and files will necessarily be at the full service of the Board in any such event. The rules which were ap-proved by the Board at its meeting on March 30, 1928, are as follows: Signed by C. S. Witherell, Chairman. (A) The authority of. the Committee on Papers and Pub-lications, hereinafter called the Committee, is defined in Art. VIII, Sec. 4 of the By-laws of the Institute, which reads as follows: "Papers and Publications: The Committee on Papers and Publications shall consist of the Secretary of the Institute, and at least twelve members of the Institute, to assist in passing on all papers offered for publication. They shall be appointed annually by the Board of Direc-tors, on recommendation of the President, and shall have authority, subject to appeal to the Board, to accept or reject papers for publication in the Transactions and Technical Publications of the Institute. The Commit-tee shall formulate a set of rules of procedure which, when approved by the Board, shall have the force of By-laws until revoked or amended." The policy of the Committee will be to uphold the ob-jects of -the Institute as set forth in the Constitution (Arti-cle 1, Sec. 2).

Jan 5, 1928

By John B. Mertie

More than 200 minerals are known that contain the rare-earths and thorium. Monazite and bastnaesite, however, are the principal commercial sources of the rare-earths, and monazite is the principal source of thorium. Monazite was in demand in earlier years mainly for its content of thorium, which was used in the manufacture of Welsbach gas mantles; but beginning in the latter part of the nineteenth century, the rare-earths became progressively more important than thorium. Recently, however, the tenor of thorium in monazite has again become a matter of commercial interest. Rare-Earths and Thorium The rare-earths proper are defined by spectroscopists as the oxides of 14 elements with atomic numbers ranging from 58 to 71; but more commonly lanthanum, with an atomic number of 57, is also included, in which case these 15 elements are often designated as the lanthanides. Chemists also include scandium and yttrium as elements of the rare-earths. A second group of elements, beginning with actinium and including thorium, protactinium, uranium, and all the transuranium elements so far produced, with atomic numbers ranging from 89 upward, are chemically and structurally related to the lanthanides, and are known as the higher rare-earths or actinides. Berzelius discovered that the lanthanides could be separated roughly into three groups, based upon the solubility of their double salts, R2(SO4)3-K2SO4-2H2O, in excess of K2SO4. This separation, with the substitution of sodium for potassium, is still used commercially. The double salts of the cerium earths were found to be almost insoluble; the terbium earths, partly soluble; and the yttrium earths, completely soluble. Based upon the degree of solubility, scandium belongs with the cerium earths; and yttrium belongs with, and gives its name to, the yttrium earths. These three groups with their atomic numbers are shown below. [ ] The prevailing state of oxidation for the rare-earths is R2O3, but cerium may readily be oxidized to the tetravalent state, in which condition it may be separated chemically from the other cerium earths. Praseodymium and terbium may also exist with the valence IV, and samarium, europium, and ytterbium may have the valence II. Most of the elements of the rare-earths, however, are very difficult to separate, and their initial isolation required the work of many chemists over a period of 150 years.20 Fractional crystallization, fractional precipitation, and ion exchange are the principal methods so far used, and fractional precipitation is now employed commercially on a large scale. Ion exchange columns are

Jan 1, 1960

By B. L. Averbach

THE rolling process may be considered as a case of a nonhomogeneous plastic flow. In such a heterogeneous deformation there is no direct general solution, and the plastic deformation varies from point to point as a function of the coordinates. It is practicable to determine these plastic strains only at the conclusion of the rolling process, and the local strains can be studied by observing the deformations produced in a suitably placed grid system. Strains at the surface of a bar after rolling have been reported by MacGregor and Coffin,' but the strain distributions within the bar have not been previously observed. Siebel² has investigated the plastic deformations resulting from wire-drawing by splitting the wire along its axis, milling a grid coordinate system on the inner plane surfaces, and binding the .wire together so that it would pull through a die as a single unit. This method was possible because of the rotational symmetry of the die. In the rolling process, however, such a system was not readily applicable. This paper describes another method of including a grid system, and reports some preliminary data on the plastic rolling strains within a square bar. Experimental Procedure 2.1 mm wide (144 network squares per sq in.) was punched from a thin lead sheet with a steel die and supported in a brass mold by thin copper wires. Pure tin was then poured around the grid to form a solid bar, with the network securely imbedded at. a given position. This bar was then machined to a square 15.2 mm (0.60 in.) wide, and then radiographed. The lead grid was quite adherent and sufficiently ductile to follow the deformation of the bar faithfully. The network lines also remained sharp enough to maintain a high radiographic contrast, and the tin bar, with the grid included, could withstand considerable deformation at room temperature without splitting at the interface. In order to fill the mold, it was necessary to cast the tin at 260-280°C and during pouring the lead grid was supported at short intervals to prevent warping. Some shrinkage cavities were encountered, but only bars which were free of shrinkage in the network region were used. This method is similar to the one employed by Steinberg" in an investigation of the strain distribution in a tensile specimen. Before rolling, the machined bars were radiographed in two directions to obtain accurate initial dimensions of each square and to observe whether the grid was straight and correctly positioned. The rolling was performed in a small hand mill with 2 in. diam rolls at room temperature, and a 20 pct reduction based on the original height was employed. The rolls were clean and no lubricant was used. Halfway through the bar, at the center of the network, the rolls were reversed and the bar extracted. These bars were then radiographed again

Jan 1, 1951

By Lester Uren

The fluid level maintained in wells pumped for oil is an important factor in deter-mining their productivity but one that has received little attention in the literature relating to petroleum-production technology. In the present paper the writer undertakes to show how and to what extent fluid level influences productivity and suggests the use of a fluid level indicator as an aid to the oil producer in maintaining the fluid surface within the well at the proper position. IT is realized that the depth of fluid maintained in a pumping well is sometimes influenced by other considerations than the quantity of fluid that will enter the well: the prevention of sand incursion, prevention of waste of natural gas, and the maintenance of a suitable submergence for the pump, for example. These latter factors have an important influence on the productivity of the well, so that otherwise unwarranted fluid levels must sometimes be maintained to offset them; but where the handling of unconsolidated sands is not a problem of consequence and where water has been properly excluded, the principles developed here and the practices recommended, should apply. The principal objective of the producer should be to produce the maximum quantity of oil in the shortest possible time. Any method or equipment that will increase the rate of production during the early years of the life of the well, when gas pressure is high, will greatly augment the .ultimate production. The maintenance of a proper fluid level in the well at all times will go far toward accomplishing this desired result. For a given set of conditions surrounding the flow of oil into a particular well, in which the viscosity of the oil, the porosity and grain size, of the sand, and the diameter of the well appear as constants, two variables determine the quantity of oil that will flow from the sand into the well. These are: the effective pressure behind or within the oil in the reservoir sand, and the fluid level maintained within the well.. The former is the expulsive force that causes movement of oil from the sand into the well, while the latter determines the magnitude of a resisting force opposing such movement. The first of these factors is largely beyond the control of the oil producer, but it is in his interest to reduce the opposing force to the lowest economic limit.

Jan 2, 1925

JESSE L. JONES,* Pittsburgh, Pa. (written discussion?).-The most important criterion on which judgment of the quality of manganese bronze can be based is its freedom from lead. Not over 0.03 per cent. of lead should be present in a good grade of manganese bronze. While it is not questioned that manganese bronze with a high tensile strength and considerable ductility can be made .from materials that will give a lead content of possibly 2 to 3 per cent., there is no doubt that such material, while it may machine readily, will be found to withstand the impact test very poorly, and hence be unsuited for high-grade engineering work. When lead is present in considerable amounts, it forms in small pools in the alloy and the material has little strength at these points; in fact, such spots in the metal are equivalent to nicks in a test bar as far as their effect on tensile strength is concerned. A further objection to a high lead content is the ease with which it oxidizes and its consequent tendency to produce dross. A second characteristic of a high-grade manganese bronze is a low content of manganese. This should not exceed 0.05 per cent.; in fact, very many of the best grades of manganese bronze show, on analysis, only a trace of manganese or no manganese whatever. Manganese is a deoxidizer and its ready oxidation protects the other metals of the alloy; but if it is present in large amounts it will produce considerable manganese dioxide, which does not separate readily from the molten alloy and may produce black specks or drossy spots and render the obtaining of clean castings difficult. Aluminum should be present in a good grade of manganese bronze in only very small amounts. A content of 0.10 per cent. aluminum is ample. Larger amounts have a tendency to increase the shrinkage of the alloy, to give the ingots and castings a white, scruffy appearance, and to prevent the beautiful, golden, oxidization color characteristic of high-grade manganese bronze and a most excellent indication of quality. The work that the author of the paper has done is valuable from a con- servation standpoint, and it will supplement, in a marked degree, the advances that have been made by a number of manufacturers of manganese bronze in utilizing the turnings from this material. A number of firms have succeeded in making a very good grade of ingot metal from turnings and other light scrap, obtaining a tensile strength and elongation

Jan 4, 1919

By Waldemar Lindgren

FIFTEEN years ago, in his presidential address before the Washington Academy of Sciences,1 Alfred H. Brooks said: "Applied geology can only maintain its present high position by continuing the researches which advance the knowledge of basic principles. Future progress in applied geology depends on progress in pure geology." Early in 1927, Dr. David White, then chairman of the Division of Geology and Geography of the National Research Council, appointed a committee "On the Processes of Ore Deposition," which was the first recognition by the Council of this branch of applied geology. This committee will not be able to solve the many complex problems involved; it can only clear the way, survey the field, state the problems and encourage systematic research. This short paper aims to outline and to analyze the present status of this kind of geological research, to ascertain the quality of the work and to suggest lines that might profitably be followed. INCREASING DEMAND FOR GEOLOGISTS Economic geology, or the art of geology, could develop only after the principles of geology and mineralogy had been established. Before that time it was merely a collection of trade rules accompanied by more or less wild speculations. Thus we observe the beginnings of economic geology in the period 1770-1820. Soon afterwards, the State Surveys were established in this country, with the realization that the natural resources should be investigated and described. Geology was hardly yet equal to the task of scientific research in relationships and genesis, however, and there followed a period of discouragement and stagnation. In the meanwhile, pure geology had again registered progress, and, based on its principles and also on the rapid mining development in the Cordilleran region, the present phase of the study of ore deposits began to take form. Raphael Pumpelly, S. F. Emmons and G. F. Becker were among the pioneers in this movement. The United States Geological Survey was organized. Ore deposits were scientifically described and studied along lines of structure and mineralogy; theories of genesis were advanced, not always permanent but based on sound induction.

Jan 1, 1928

By M. Muskat

Calculations are reported on the differential sensitivity of the updip invasion of oil strata of varving permeability to the driving pressure differential. It is assumed that the water-oil interfaces advance with sharp fronts, or that the microscopic displacement efficiency is independent of rate and capillary pressure effects. It is found that, under such conditions, limitations of withdrawal rates will not greatly inhibit the "fingering" and bypassing tendency through high permeability strata unless the differential fluid head across the original oil column is of the order of or exceeds about 80 per cent of the driving pressure differential. In practice, such restrictions will be feasible only for oil reservoirs and aquifers of high permeability and dip, but may develop automatically under combined gas injection and water drive operations. INTRODUCTION A commonly expressed view regarding the intrusion of edge-waters into oil producing formations is that the geometry of such advance is rate sensitive. Specifically, it has been suggested that high rates of advance, stimulated by rapid withdrawals, will lead to "fingering" and an irregular type of invasion, whereas at low withdrawal rates the water encroachment will be more uniform. Two factors tend to support this view. One is the resultant effect of capillary pressure and gravity gradients in the displacement processes' involved in water intrusion, which are magnified at low rates of flow so as to improve the recovery efficiency. The other is the direct retarding effect of the rising water head as it advances upslope into the producing area. Capillary pressure forces give rise to a rate sensitivity of the oil recovery by water displacement in uniform strata as well as differential effects in non-uniform formations. These are basically independent of the effect of gravity and would also occur in horizontal beds or when the oil and water have the same density. Unfortunately, however, the fundamental equation describing the displacement process under the action of capillary pressures can be solved only by numerical or graphical procedures, and moreover the solutions are sensitive to the character of the capillary pressure and relative permeability curves.* On the other hand, the direct effect of gravity can be given a formal analytical solution if the simplifying assumption is introduced that the water advances with sharp fronts in the individual uniform strata. It depends on the absolute permeabilities of the water invaded zones and hence results in a rate sensitivity of the differential invasion in stratified media. Although a tieatment of this factor alone will not give a complete evaluation of the effect of rate on water intrusion in non-uniform pays, it should provide at least a semiquantitative measure of the sensitivity of "fingering" to withdrawal rate. Such a treatment will be presented in the following sections. GENERAL THEORY The basic element of the theory is the history of water advance updip in a uniform stratum (Fig. 1). In contrast to the assumption of constant flow rate, generally made in the analysis of displacement processes, we shall assume here that

Jan 1, 1951

By H. J. Rahilly

Mine fires, in the Butte district, have been a source of trouble and expense for the past thirty years, for while the actual fire area in most of the mines has been comparatively small, the handling of the gas has generally been a much larger problem than the actual putting out of the fire. The chief causes of these fires have been: Defective electrical equipment, incendiarism or carelessness, and spontaneous combustion. While fires from the first two causes have been numerous, they have generally been discovered and extinguished before they became very serious. Spontaneous combustion has been the cause of most of the large fires. Sufficient heat has been generated by ground movement, high rock temperatures, and decomposition to set fire to inflammable materials (tarred ropes, canvas, dry timber, manure, and hay) left in the gobs some years ago. Also, the heat resulting from the oxidation of the fine broken sulfide ore is sometimes sufficient to set fire to the timbers. In 1906, a fire was discovered on the 1100-ft. level of the Minnie Healy mine about 400 ft. (122 m.) west of the Minnie Healy shaft, which presumably originated, in one of the upper levels, from spontaneous combustion. The fire was walled off by concrete bulkheads and a pillar of ground 100 ft. (30 m.) thick was left below and mining resumed underneath. During subsequent operations, this pillar became cracked and broken and the fire passed into the new workings. It travelled downward and spread rapidly until, in 1917, it had become necessary to wall off portions of the Tramway, Leonard, and West Colusa mines on the 1300, 1400, 1500, 1600, 1800, 1900, and 2000-ft. levels, and the tops of the 2200-ft. raises were sealed. The fire area now consists roughly of a block 1000 by 1200 ft. and from the 600-ft. to the 2200-ft. level. This block is composed largely of a series of parallel northwest-southeast nearly vertical veins and stringers that form a large orebody, with no well-defined walls but badly fractured and faulted, and known locally as "horsetail ore." These veins, or orebodies, are mined by the square-set or the rill method.

Jan 1, 1923

By P. W. Ramsey, D. P. Kedzie

INCREASING demand for improved strength-weight ratios made on aircraft structures has resulted in a gradual increase in the tensile strength requirements for steels used in such applications. As the cyclic loads often are more critical than static loads, and the fatigue properties are generally the design criteria, the question arises as to whether an improvement in fatigue properties accompanies the increased tensile strength. The present investigation was undertaken to determine the relationship between fatigue and tensile properties for an aircraft quality steel in the 155 to 280 ksi (1000 psi) tensile strength range, using the Prot method of fatigue testing. Procedure and Results After preliminary work to establish proper heat treating procedures for this heat of aircraft quality electric furnace steel (a Ni-Cr-Mo-V steel," AMS- Prot Fatigue Testing Method—The determination of the endurance limit by the conventional Wohler method can be time-consuming and easily require 20 specimens when statistical variance is to be established. This is also true when endurance limit loads are determined on actual parts or subassem-blies, and the desirability of a reliable accelerated method has been evident for some time. The primary advantage of the Prot method of fatigue testing is in reducing the number of specimens and the time required for each test. Unlike the Wohler method, every Prot specimen tested con- tributes to the determination of the endurance limit, and the authors have been able to duplicate Wohler results obtained with 20 specimens with only half the specimens and a fourth of the total cycles. This new technique for defining the endurance limit was proposed in 1948' by Marcel Prot and consists of progressively increasing cyclic stress until fatigue failure occurs. By varying the load rate, a, a useful relationship is found to exist with failure stress, so that for steel the failure stress appears to

Jan 1, 1958

By Eric S. Cheney

Sulfur isotopes are best used in conjunction with other geological studies to determine the origin of known deposits; concept-oriented exploration programs can then be developed to find similar deposits. Geochemical processes are capable of causing different S '41S" ratios in the minerals and fluids participating in natural reactions. Because the magnitude of the resultant isotopic difference is inversely proportional to temperature, sulfur isotopic studies can be used to determine the source of the sulfur in high temperature deposits. The narrow spread of sulfur isotopic values from ores related to cupolas of felsic intrusions suggests that the sulfur in the ore-forming fluids was derived from a fairly uniform source (such as the intrusions) rather than by heated ground water from the adjacent country rocks. However, geologic and isotopic evidence suggest that the sulfur of many nickel sulfide ores may have been derived from the country rocks rather than the associated mafic igneous rocks. This sulfurization hypothesis implies that mafic intrusions in sulfur-rich country rocks should be prime exploration targets. Sulfur isotopic analyses of sulfides in the mafic rocks may indicate whether sulfurization has occurred. In equilibrium geochemical reactions S" is concentrated in the minerals with the greater bonding strengths. Thus the isotopic compositions of coprecipitated sulfides that have not undergone exsolution may be used as geothermometers and to distinguish multiple periods of mineralization, post-ore metamorphism, etc. The sulfur isotopic compositions of coexisting sulfides at Butte, Mont., indicate that the copper minerals did not originate by simple replacement of pyrite. Geologic and isotopic evidence suggest that the mineralogical and isotopic zoning at Butte formed almost isothermally during the geochemical evolution of the ore-forming fluids upward and outward from the Central zone. Unidirectional reactions cause enrichment of S" in the products. At low temperatures the isotopic effects of bacterial and inorganic reactions are difficult to distinguish. Anaerobic sulfate-reducing bacteria apparently were responsible for the sulfur of Gulf Coast salt domes and for diagenetic pyrite in sandstone-type uranium deposits. Sulfur (and carbon) isotopic data suggest that the roll ore bodies of sandstone-type uranium deposits originated by limited inorganic oxidation of diagenetic pyrite rather than by bacterial activity. Accordingly roll ore bodies should be most numerous and thickest against those portions of the sandstone aquifer that contain pre-ore pyrite.

Jan 1, 1975

By M. E. Lombardi

THE Coalinga oil field is located on the west side of the San Joaquin Valley, California. The structure is in general a monocline, the edges of the oil horizon resting on the foot hills and dipping gently toward the east. One prominent anticline occurs plunging southeast. The earlier drilling was done in the foot hills comparatively near the outcrop and the wells were shallow. The sands were followed eastward and, in the case of the anticline, along the plunge, the wells becoming deeper and deeper until the depth of 4,000 ft. was reached and passed. There is nothing to show that the oil will not be found in quantity at still greater depth. In fact, some of the best producers have tapped the sand at close to 4,000 ft. The recovery of oil still farther to the east, and therefore at greater depth, seems to be mainly a question of drilling. In this territory the formations drilled through are chiefly sands and shales; they will not "stand up" in an open drilling hole; the casing has to be carried close to the bit, and it is always difficult to keep the casing free for any considerable distance. Ability to carry casing of comparatively large diameter without conductor pipes for distances of 2,000 or 3,000 ft. or over is desirable in such territory chiefly for two reasons. It makes it possible to enter the oil sand with a pipe of ample diameter; it eliminates one or more expensive strings of casing which act only as conductors for the water string, and furthermore, in territory where waters are encountered which corrode steel rapidly, it makes possible the construction of a rust- and alkali-resisting water string. It is always desirable to shut off top waters, which may lie within 100 ft. or less of the oil sand, with 10-in. pipe. Where the depth is so great that a practical weight of 10-in. pipe will not withstand the probable collapsing pressures, 8 ¼ in. at least is desirable. About the limit of rotary drilling to date in California seems to be the setting of the 10-in. string at 3,200 ft., although the rapid advance in rotary work during the past year seems to indicate that this depth may soon be increased. It is my purpose now, however, to treat only of cable-tool drilling.

Jan 2, 1915

By Ernest A. Hersam

Accurate ore-sizing with screens is drawing attention to certain details that now, more than ever before, require attention. There are many tests that must be preceded by careful sizing. The assayer often could profit by a more careful selection of screens. In milling, more attention is given the slimes produced. Cement-manufacturers are pulverizing and screening finer than they formerly did, and others are reducing materials to fine sizes at high cost, with screens used to govern the fineness of the pulverized product. Fine screens are expensive, easily injured by misuse, are carried in stock sparingly by most dealers, and are handled often by those who know little about them except their designated number. More attention, on the whole, needs be given the actual size of the mesh-openings, and less emphasis placed upon any custom or conventionality in numbering. An effort to classify wire screens, in this respect, leads at once into computations, where one is confronted with details of sizes and standards, of different wires, different gauges, and different customs. There is always uncertainty about the exact working-size of a screen until one gives the matter special attention, and devotes more time to it than its simplicity seems to demand. To know only the number is not sufficient for all uses. Often, in sets, superfluous sizes are used; and sizes are omitted that are of critical importance. In wire screens, the use of different standard sizes of wire makes important differences in dimensions that must be taken into account. The dealer usually grades screens by the number of openings per linear dimensions, regardless of the size of the openings or of the wire. Certain 100-mesh screens in use are found, by measurement, to be actually coarser than others of 90-mesh, a result which is due, of course, to the use of larger

Jan 1, 1907

By P. Nicholls

PATENT records show that the attempt to improve the burning of fuel by mixture or pretreatment with chemicals dates back to the early years of the last century. By 1845 English and French patents had included the specific beneficiations of elimination or reduction of smoke, soot and clinker; reduction of the ashes; elimination of sulphur fumes; increase of the rate of burning; increase of the time a given charge of fuel would last; and, in most patents, a saving of fuel. The earlier patents specified additions up to 80 lb. or more per ton of fuel, but after 1860 the quantity was seldom more than 4 lb. There is no record of the extent to which these patents were commercialized, but after 1874 many American patents were assigned to companies specializing in treatment of coal, so it is probable that the products were marketed on a considerable scale at least as early as that date. From 1900 on, many proprietary products were marketed under the general name of "fuel savers," the principal sales being in small packages for the use of householders; savings of from 10 to 40 per cent of the coal were promised. Starting with 1927, the use of proprietary or other mixtures of chemicals was extended to power plants and to treatment of coals at the mines, the claims of saving of fuel being subordinated to those of general improvement and, in particular, to reduction of clinkering. Such expectations are attractive and a number of companies experi-mented with or adopted the practice. There were reports of improved operation, but, apparently, few were confident enough that these improvements were due to the salts to publish the results of tests or their records of operation. There are no data on the yearly tonnage of coal treated but indirect reports suggest that it has been relatively large. Since its establishment in 1910, the U. S. Bureau of Mines has con-tinually received inquiries about these products. At the request of. other governmental departments it made tests in 1910, 1916 and 1930, using certain proprietary products applied according to the instructions of the vendors; these tests were made with eastern coals in domestic and

Jan 1, 1937

By C. A. Heiland

The Eötvös torsion balance permits the measurement of certain second derivatives of the gravity-potential, which are known as the gradients of gravity and the curvature values for an equipotential plane of gravity. These quantities are influenced on level ground by the configuration of the masses underneath. Hence, the torsion balance has gained great importance for the location of geological structures and thus indirectly for the discovery of oil and other mineral deposits. If the ground is not level, however, the measurements become more difficult, because the superficial mass-irregularities also produce more or less considerable disturbances. It is necessary, therefore, to determine the shape of the surrounding topography by leveling as well as by consulting topographic maps and to compute its influence upon the torsion balance. The correction thus determined is called, in general, the topographic correction; it is composed of two constituents, the terrain correction and the cartographic correction. The terrain correction would be that part of the topographic correction as derived from the direct leveling of the area surrounding the station, whereas the data for the computation of the cartographic correction are obtained from a topographic map, usually beginning with a radius of LOO meters, as under most circumstances it is difficult to level along a arger concentric circle about the station. Principle of Topographic Correction The principle of all topographic corrections is to assume a homogene-ous compositon of the masses around the station in regard to specific gravity as well as a mathematical shape of the topography. The results become the more accurate the closer this mathematical shape is to the actual configuration of the terrain, but naturally the amount of necessary computation also increases. If a standard correction with fixed dis-ances is adopted, the middle error of this method will, therefore, increase as the irregularity of the terrain. Hence, the application of the torsion balance in mountainous areas may be successful only if the disturbances due to heavy masses underneath the surface are so large as to exceed onsiderably the increased middle error due to rugged topography, or,

Jan 1, 1929

By H. J. Modi, P. L. De Bruyn

IN recent years interest has been aroused in flotation rate studies both from a technical and a more practical aspect. With increasing fineness of grind becoming a necessity in treatment of low grade ores, difference:; in flotation rates of various size ranges will assume importance in the evaluation of overall recovery results. Theoretical analysis of flotation kinetics was initiated by Schuhmann,' who sought to define flotation rate of a given mineral and specified size range in terms of certain physical variables of the flotation system. Using as a basis for his analysis the bubble-particle encounter hypothesis previously advanced by Gaudin,' Schuhmann writes for the rate of flotation (R,.) of particles of average size x, Rx = PcPa(x) V F. [1] In this relation Pc and Pa represent, respectively, the probability of collision between particle and gas bubble in a given time interval and the probability of adhesion of particle to the bubble after collision. Rigorously speaking, the term PC does not have the significance of a probability factor, since it depends on the time interval and therefore can be numerically greater than unity. The term c(x) expresses the concentration of particles of an average size x in the flotation cell in weight per unit volume of pulp, and V denotes the total volume of pulp in the cell. The product, P,c(x)V, defines the frequency of particle-bubble collisl.on, and when it is multiplied by P,, the number of collisions per unit time resulting in successful adherence is obtained. The factor, F, measures the froth stability and is introduced because after fruitful bubble-particle contact some particles may still riot reach the froth launder. Coalescence of bubbles in the froth column or too short a bubble life could account for this effect. Schuhmann also introduced the concept of "specific flotation rate" (Q) to allow for the relative abundance of different mineral species in the flotation pulp. The specific flotation rate, having the dimension of reciprocal time, is defined as Eq. 2: Qx =Rx/c(x)v [2] and it also follows from Eq. 1 that Qx = PcPaF. [31 The theoretical aspects of flotation kinetics were also considered by Sutherland,3 who tried to improve Eq. 1 by expressing the probability factors in terms of such physical variables as particle radius (x), bubble radius (X), velocity of bubble relative to particle (v), the number of bubbles per unit volume of pulp (N) and the induction period (A) necessary for air-mineral adhesion. According to Sutherland's treatment, the rate equation, Eq. 1, transforms to R, = [3pX x v N] [sech2 (3 v ?/4 X) ] ?c(x) V [4] where the first term in brackets on the right-hand

Jan 1, 1957

By William S. Hannan, H. Rush Spedden

Flotation may be defined as a process whereby mineral particles are concentrated by selective adhesion to air-liquid interfaces. The process involves attachment of desired mineral particles to air bubbles, and removal of the mineralized air bubbles from the surface of the pulp as a mineral concentrate. Problem Although great strides have been made in understanding the principles of flotation, one part of the process which has not been adequately explained is the mechanism by which selected mineral particles become attached to air bubbles. A glance at the froth of an operating flotation cell demonstrates adequately that use of proper reagents and conditions mill result in such attachments; but how such attachment takes place is not definitely known. A better knowledge of this factor might lead to improved flotation practice either through altered machine design or the application of scientific innovations. Direct observation of the behavior of mineral particles and bubbles in an operating cell does not appear promising because of the complexity of the system. For this reason, conclusions concerning the problem must be deduced from theoretical considerations or from observation of simplified systems designed to reproduce conditions thought to exist in an operating cell. Present Theories Two mechanisms have been recognized as fundamental in particle-bubble attachment: gas precipitation and direct encounter. It is a simple matter to demonstrate in the laboratory that attachment can be brought about by either mechanism. As to the relative importance of the two in a particular flotation system, however, there is a divergence of views. Taggart1 states, Under exceptional circumstances sufficient force and time to effect attachment may conjoin in an ore pulp undergoing agitation, and a preformed bubble adhere to a collector-coated mineral particle, but the occurrence is rare. . . . Pulp-body froth flotation effects selection in the body of a conditioned pulp by causing gas bubbles to precipitate from solution in the liquid phase preferentially at the surfaces of collector-coated particles, and to cling to these particles, Gaudin2 states that, within the pulp body of an agitation machine, attachment of mineral particles to air bubbles occurs as a consequence of contact between the two. This theory has been supported by theoretical reasoning and much circumstantial evidence. Perhaps the most interesting bit of evidence in favor Of this theory js the difficulty in the flotation of fines. If attach-

Jan 1, 1949

By D. Turnbull

RECENTLY it has been shown that aggregates of small liquid droplets of tin,' mercury' or gallium' kept from intercommunicating by suitable films do not solidify at an appreciable rate unless the supercooling is very much greater than that usually necessary to cause a large continuous mass of the metal to solidify. For example oxide-coated tin droplets1 (1 to 10 micron diam) must be supercooled 100" to 110°C before their rate of solidification becomes rapid, although large continuous masses of liquid tin usually begin to solidify when supercooled 30" or less." These experiments have been interpreted' on the hypothesis that nucleation of crystals in large continuous metal samples is almost always catalyzed by accidental inclusions. Therefore, if the metal is dispersed into a number of isolated droplets large in comparison with the number of inclusions, most of the droplets should not crystallize until a temperature sufficiently below the thermodynamic melt- ing point, T0, has been reached to permit an ap-preciable rate of homogeneous (noncatalyzed) nu-cleation. In general this temperature is very much less than the temperature at which the rate of heterogeneous (catalyzed) nucleation is appreciable. If this interpretation is correct then investigation of the kinetics of crystallization of small droplet aggregates should be one of the most fruitful methods of obtaining information about the homogeneous formation of crystal nuclei in liquids. In this paper the results obtained on gallium and mercury are reported more fully. In addition, results on the supercooling of aggregates of liquid bismuth and lead droplets are included. Experimental Procedure Some care must be exercised in the choice of a barrier to prevent the liquid droplets from coalescing lest the barrier itself catalyze the formation of crystal nuclei. From this standpoint, the most desirable barrier is vacuum or inert gas, but, because of the difficulty of experimental arrangement, solid compounds and adsorbed films have been selected. There are two guiding principles in the selection of compounds as barriers in addition to the requirement that they prevent coalescence of liquid droplets. First, the compound should be almost insoluble in the liquid metal and second, its lattice structure should be quite unlike that of the forming metal crystal. Even so, there is no a priori assurance that the solid compound film will not catalyze to some extent the formation of metal crystal nuclei. An adsorbed protective monolayer is less likely to be catalytic than a crystal compound film, but it is not often possible to find a monolayer that is stable under the experimental conditions. Also, it is desirable, though not generally essential, that the aggregate of droplets be prepared by breaking up the massive metal rather than from a powdered compound of the metal.

Jan 1, 1951

By Louis Ware

At the beginning of the present war, the United States faced the need to multiply its production of magnesium metal almost roo times within the shortest possible period. Urgently needed for construction of military aircraft, incendiary bombs, and other war uses, magnesium was at the top of the list of critical war materials. Up to that time only one Producer, employing Only One process and using One raw material in a single plant, represented this country's entire Production capacity. It was immediately desirable to plan a numher of plants located strategically over the Count'Y and to expand an industry more rapidly and to a greater extent than ever before had been attempted in so short a time. In '939 this American producer, the Dow Chemical .9 was making about 7 million Pounds of magnesium metal. It utilized as a raw material brine containing magnesium chloride, which was pumped from wells in Michigan. The logical ap-preach to certain increased production was to employ the same process on the same raw material in other sections of the United States. In Europe and other countries, different processes had been used and different raw materials were being utilized, but all of the skill and knowledge for production in this country was that of using the Dow type of cell and magnesium chloride as a raw material. The Government was testing other processes, but none then had been proved commercially feasible. Development OF New Process The International Minerals and Chemical Corporation had available a large quantity of magnesium ,chloride at Carls-bad, New Mexico, contained in the end liquor produced from its potash plant sillce the buildng of the plant in 1941 It was the only company mining commercially a magnesium ore and having anything like this quantity of magnesium chloride liquor. The magnesium ore, langbeinite, was being mined from the 800-ft. level for its content of potassium sulphate. This ore, a potassium magnesium sulphate, was reacted in a base exchange plant with potassium chloride to produce potassium sulphate, the discharge liquor having a high content of magnesium chloride. Three potash-producing companies are in the Carlsbad area, but only International has developed and is commercially producing the potash-magnesium ores. The lower, or No. 4, veil, in that area is potassium chloride ore, and is continuous through all the properties. The langbeinite, or No. 2, vein is minable at the International property, but occurs sparsely, if - at in other areas being mined in that vicinity. It is understood that most of the mag. nesium produced] by Germany comes from magnesium and magnesium-potassium ores obtained from potash mines. It was logical for International to pro-pose to make available this magnesium material and to offer its technical staff to design, construct and manage a magnesium plant for the account of the Government. The plan that finally was adopted by the

Jan 1, 1944

By H. N. Eavenson

The eleven mines of the United States Coal and Coke Co. in the Pocahontas coal field are situated in McDowell County, W. Va., which is a mountainous region. The valleys rarely exceed 200 ft. (60 m.) in width, the hillsides slope from 25°to 33°, and the tops, from 600 to 900 ft. above the valleys, carry practically no level land. At least 80 per cent. of the area is covered with timber. All the workings are drift mines; and while the average grades of the seams worked are ample for drainage, local dips and swamps necessitate the use of a large number of local pumps or of numerous drainage ditches to keep the mines free from water during heavy rains. The water handled in any mine is not great, compared with the coal output, and usually causes little trouble except during extremely wet periods. In new workings, the water encountered, except in rare cases, is trifling; it is only after rib drawing has started and the surface has been broken that water troubles begin. The strata overlying the coal are sandstone, shales, and slates; as the soil is thin and sandy, it does not tend to puddle and stop the cracks, which remain open for a long time. As mining progresses and the robbed area increases, the broken area becomes larger, increasing the openings into the mined territory. The cover over the robbed portions of the mines varies from 30 to 750 ft. (9 to 228 m.). When the ground is saturated, considerable water finds its way into the mines the day after a heavy rainfall and for three or four days it tends to fill the low places, wash the tracks, etc. and unless from three to four times as many pumps are installed as are normally needed, considerable output is lost. In most cases the water will flow from the mines, and the obvious solution is to provide drainage ditches of ample size to carry the maximum flow expected, so that the inflow will have no opportunity to flood the working places. Laying out the drainage headings on the proper average grades was an easy matter but where blasting was necessary to provide uniform grades, as was frequently the case, it was important that the maximum flow to be expected and the size of ditches to be provided should be known so that only rock work necessary to provide proper drainage

Jan 1, 1922